util
Class PersistentMap

java.lang.Object
  |
  +--java.util.AbstractMap
        |
        +--util.PersistentMap

public class PersistentMap

extends AbstractMap

A persistent hashtable (Map), which in this case maps to a SQL database.

This is based on AbstractMap, and for the most part is using AbstractMap's methods for doing lookups. This means that hash access is probably unbelievably slow, so using this for speed-critical code will probably not make you happy.

Developer's Note: This is probably more correct anyway, since for lookups we want to compare every item in the hashtable against the test object using the equals() method in order to be sure we've got the right thing.

Field Summary

protected String

tableName

Constructor Summary

PersistentMap(AgentID aid, String tabname, Connection cnxn)
This constructor works like the regular one except that it creates a table name specific to the agent instance.

PersistentMap(String tabname, Connection cnxn)
Creates a new persistent map file.

Method Summary

void	destroy() Destroy the underlying table.
Set	entrySet() Get all map entries as a set.
protected int	execSQL(String s)
protected int	execSQL(String s, boolean loud)
static void	main(String[] args)
Object	put(Object k, Object v) Put a new value into the database.
protected ResultSet	querySQL(String s) Helper function to execute queries with automatic reconnection.
protected ResultSet	querySQL(String s, boolean loud)

Methods inherited from class java.util.AbstractMap

clear, containsKey, containsValue, equals, get, hashCode, isEmpty, keySet, putAll, remove, size, toString, values

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

tableName

protected String tableName

Constructor Detail

PersistentMap

public PersistentMap(String tabname,
                     Connection cnxn)

Creates a new persistent map file. Takes a designation and a database connection to create the table on the back-end. If the table already exists, the class will assume that it holds old data. If the existing table is of the wrong format, expect a large number of exceptions.

Parameters:

tabname - The name of the map. This is used to create a database table (any non-alphanumeric characters will be changed to underscores so that SQL doesn't choke on it).

cnxn - The database connection url. See the java.sql Connection class for more information.

PersistentMap

public PersistentMap(AgentID aid,
                     String tabname,
                     Connection cnxn)

This constructor works like the regular one except that it creates a table name specific to the agent instance. Takes into account all parts of the agentID: society, occupation and designation.

Parameters:

aid - an AgentID value

tabname - a String value

cnxn - a Connection value

Method Detail

entrySet

public Set entrySet()

Get all map entries as a set. Users of this class can use the set's iterator to get all the entry information, or can use AbstractMap's access methods to make their lives easier.

Overrides:

entrySet in class AbstractMap

put

public Object put(Object k,
                  Object v)

Put a new value into the database. As of this version, this doesn't look up the old value, and just returns null, so applications that are dependent on the old value should probably do a get() beforehand.

Overrides:

put in class AbstractMap

destroy

public void destroy()

Destroy the underlying table. This method should probably be rarely (if ever) called, since it gets rid of the very thing that makes this persistent data. If any other methods are called after this one, they will probably spew exceptions to the standard error stream.

execSQL

protected int execSQL(String s)

execSQL

protected int execSQL(String s,
                      boolean loud)

querySQL

protected ResultSet querySQL(String s)

Helper function to execute queries with automatic reconnection.

querySQL

protected ResultSet querySQL(String s,
                             boolean loud)

main

public static void main(String[] args)